This invention is related to a coating composition comprising an anhydride-containing polymer and an epoxy-containing polymer, which polymers are co-reactive and capable of forming a cured coating on a variety of substrates. More particularly, this invention is directed to a multicomponent composition in which the epoxy-containing polymer component is structured for improved properties.
There are a variety of epoxy/anhydride multicomponent coating compositions available for coating or finishing substrates. Typically, the components of such compositions are mixed together before application and then the resulting composition is applied by conventional techniques such as spraying. The composition is then cured, either at ambient or elevated temperatures. These compositions may be used as a finish for original equipment, particularly automobiles and trucks, or as a refinish for the same. Such compositions may also be used to paint bridges, buildings, appliances, metal cabinets and other assorted structures.
Representative compositions are disclosed in the following patents:
U.S. Pat. No. 4,507,411 discloses a two component composition comprising a glycidyl or epoxy-containing component which, in the presence of an amine, alcohol, ketimine, acetal or oxazolidine, cures at ambient temperatures.
European Patent Application 0,123,793 discloses a two component composition comprising a first component, which has an anhydride ring opened with an amine, and a second component, which contains glycidyl groups.
U.S. Pat. No. 3,136,736 and British patent 994,881 disclose coating compositions comprising polyepoxides and maleic anhydride copolymers.
U.S. Pat. No. 4,732,791 discloses a coating composition comprising polyepoxides, a monomeric anhydride curing agent and a low number average molecular weight hydroxyl group containing polyfunctional material.
Although anhydride-epoxy compositions are generally known, there is a need for a coating composition with improved properties. In general, coating compositions, in order to be useful as an exterior finish or refinish for a variety of substrates including automobiles and trucks, should have excellent adhesion to the substrate to which it is applied, good outdoor weatherability, and excellent appearance.
Furthermore, because of environmental concerns about volatile organic components (VOC's) there is a need for a coating composition with a high solids and low volatile organic content which retains its sprayability. In addition, such a coating composition should exhibit an excellent mix of other desirable coating composition qualities such as pot life, viscosity, compatibility with the basecoat, and rate of curing. The cured coating must also have hardness and durability.